1. Field of the Invention
The present invention relates to a TAB (Tape Automated Bonding) tape and a manufacturing method therefor.
2. Description of the Related Art
In accordance with a demand of high-density mounting and a demand of increased speed of signal processing in electronic devices, there has been advanced a bare chip mounting technology such that an IC (Integrated Circuit) chip is directly mounted on a substrate or the like. As an example of the bare chip mounting technology, a TAB (Tape Automated Bonding) process is known. The TAB process employs a TAB tape constituted of an insulating tape member and a plurality of leads or fingers formed on the tape member. The tape member has a plurality of sprocket holes formed along opposite side edges like a movie film. The IC chip is connected to the TAB tape by inner lead bonding, and thereafter an outer peripheral portion of each lead of the TAB tape is connected to a conductor pattern on the substrate by outer lead bonding.
The tape member is normally formed from an elongated polyimide film. The use of such an elongated film enables the TAB tape to be wound around a reel, which will become useful for rationalization in a mounting step. Furthermore, according to the TAB process, it is advantageous that a pitch of bonding portions can be reduced and that an increase in size of the chip with an increase in the number of terminals can be met.
Conventionally, metal bumps formed on electrodes on the chip are bonded to each lead of the TAB tape. However, since it is difficult to form the metal bumps on the chip, there has recently been developed a method of forming the metal bumps on each lead rather than on the chip. The metal bumps are formed in order to make the bonding easy and prevent breakage or the like of the IC chip in bonding. An example of the method of forming the metal bumps on each lead of the TAB tape in the prior art is to deposit a bonding metal on a surface of each lead at predetermined positions by plating.
However, the formation of the metal bumps by plating requires a costly plating equipment. Furthermore, a process is complicated to require an advanced technique.